3B Scientific SW String Pendulum Set - Manual (Page 2)

2
4. Functioning principle
In a stationary position, the only forces acting on
the hook of the dynamometer are those of the
opposing tension springs (cf. Fig. 2). All motion
of the string pendulum about the effectively sta-
ble eyelet hole from which it is suspended is
resolved into two vectors and detected by the
dynamic force sensors. For small angles, the
output voltage from the amplifier board is almost
proportional to the deflection of the pendulum
(cf. Fig. 5).
A circular motion of the pendulum creates sinu-
soidal AC voltages at both amplifier outputs,
which are out of phase with one another by 90°or
-90° depending on the direction of rotation.
5. Operation
5.1 General information
The following additional equipment is necessary
in order to carry out the experiments:
1 SW stand equipment set
1012849
1 SW sensors set (@230V) 1012850
or
1 SW sensors set (@115V)
1012851
1 USB oscilloscope 2x 50 MHz 1017264
1 PC, operating system Win XP, Vista, Win 7
or
1 Analogue oscilloscope 2x 30 MHz 1002727
Caution: Dynamic force sensors must not be
subjected to mechanical overloading
• Neither sensor hook may be loaded with
more than 5N in the axial direction and 1 N
in transverse direction.
• Be especially careful with the maximum load-
ing force when assembling the system or
suspending loops or springs from the hook.
• Make sure stand rods are firmly fitted into
the base and that all other mounting ele-
ments are also firmly fitted to the stands.
5.2 Set-up for string pendulum
• Screw the stand rods with both external and
internal threads into the outer threaded
sockets of the base plate.
• Extend both rods by screwing rods with ex-
ternal thread only onto the ends of them.
• Attach double clamps near the top of both
stand rods and turn them to point inwards so
that the slots are vertical and facing one an-
other.
• Attach both springs from the spring module
to the lugs on the cross bar (angled side).
• Hang the large loop of string from the lug on
the flat side.
Fig. 1 Assembly of spring module
• Connect the springs and vector plate to the
hook of a dynamic force sensor with a small
loop of string and carefully pull everything
taut.
• Attach the force sensor with the screw tight-
ened by hand.
• Attach the second force sensor in the same
way.
Fig. 2 Attachment of dynamic force sensors to spring
module
• Pull the string through the eyelet of the spring
module (in the middle of the metal disc).
• Thread the end of the string through the two
holes of the length adjustment slider.